Doping TiO2 by Cr from tannery wastewater for improving its activity under visible light in the dye degradation

Authors

• Endang Tri Wahyuni * ^{1, 2}
• Sri Wahyuni ^{1, 2}
• Mandrea Nora ^{1, 2}
• Novianti Dwi Lestari ^{1, 2}
• Suherman Suherman ^{1, 2}

1. Chemistry Department, Faculty of Mathematics and Natural Sciences, Yogyakarta, Universitas Gadjah Mada
2. Sekip Utara POB Bls 21, Yogyakarta, Indonesia, 55284

Abstract

This paper deals with the comparison of the Cr (III) dopant from tannery wastewater to the Cr (III) from the pure salt solution on the character and activity of TiO₂. The doping was conducted by hydrothermal method, and the Cr-doped TiO₂ prepared was characterized by UV specular reflectance (SRUV), X-ray diffraction (XRD), and X-ray fluorescence instruments. The effect of the Cr (III) doping on the activity of the TiO₂ was evaluated by Congo red photodegradation. The research results reveal that Cr (III) doping on TiO₂ has been successfully reducing remarkably the band gap energy (Eg) from 3.13 eV to 2.64 eV, shifting into the visible region, and further noticeably improving TiO₂ activity. The effect of the Cr (III) doping from the wastewater is found to be slightly higher than that of the salt solution. The highest degradation of 10 mg/L Congo red in 50 mL solution, can be reached by applying 30 mg of the photocatalyst in 60 mins and at pH 7.

Highlights

• A comparison of Cr-doped TiO₂ activity from Cr(III) tannery wastewater and pure salt has been studied.
• Cr(III) doping on TiO₂ reduce the band gap energy and improve TiO₂ activity under visible light.
• The activity of TiO₂-Cr from the wastewater was found to be slightly higher than that of pure salt.
• Hazardous tannery wastewater containing high Cr(III) concentration can be converted into useful material, such as dopan TiO₂

Graphical Abstract

Keywords

• Congo red dye
• Cr
• Doping
• Photodegradation
• Tannery wastewater
• TiO2